The present invention relates to an X-Y input device, and more particularly to an X-Y input device suitable for use as a graphics input device associated with a graphic display apparatus.
Graphic display apparatus are basically composed of a display screen, a display controller, a data channel, and an input device which may be in various forms. One known input device is a "joystick" having a lever supported by a gimbal mechanism and tiltable by the operator in any direction of a plane. A control device detects the direction and angle of tilt of the lever and generates voltages or digital signals indicative of coordinate values in X and Y directions. This type of input device is disadvantageous however in that the range of angular movement of the lever is limited and data signals entered by the operator are relatively unstable.
In an effort to eliminate the above shortcomings, there has been developed an input device called a "mouse". One type of the mouse has a rotatable member such as a steel ball (hereinafter referred to as a "ball"), a first driven roller held in contact with the ball and rotatable in response to rotation thereof, and a second driven roller held in contact with the ball and rotatable in response to rotation thereof. The first and second rollers have their axes of rotation extending substantially perpendicularly to each other. The mouse also includes first and second angle detector means composed of variable resistors or encoders for separately detecting angles of rotation of the first and second driven rollers. The ball, first and second driven rollers, and first and second angle detector means are all housed in a casing.
The casing has an opening defined in its bottom with the ball partly projecting through the opening. In use, the casing is held by the operator to place the ball against a given surface. By moving the case to cause the ball to roll on the surface in any desired two-dimensional directions, the first and second driven rollers are rotated about their own axes in directions and through angles dependent on the rolling movement of the ball. The directions and angles of rotation of the driven rollers are converted by the first and second angle detector means into voltages or digital signals representative of coordinate values in X and Y directions. The generated signals are then entered into a display apparatus.